The present invention relates to a translation method for communication between speakers of different languages and to a system implementing the same wherein speakers using different languages can communicate with each other through translation means of the respective languages combined to communication means such as telephone sets or electronic mail.
Heretofore, there have been proposed automatic translation methods in which translation of a sentence expressed in a natural language into another natural language is achieved by an apparatus such as a computer. For example, according to an automatic translation method described in an article of Nitta et al. "U.S. Pat. No. 4,641,264 dated Feb. 3, 1987 entitled "Method For Automatic Translation Between Natural Languages" (U.S. patent application Ser. No. 415,601) and assigned to the same assignee with the present application (corresponding to JP-A-58-40684) operations for the translation such as a syntactic analysis are accomplished by a computer to translate a sentence of a first language into a second language. In accordance with the method above, the translation is conducted in a one-directional procedure, namely, from the first language to the second language.
A bi-directional translation procedure is achieved, for example, in a communication system with translating function described in the JP-A-1-147774. In this system, a recognition result of inputted speech is translated into a language of a communicating partner and then a translated sentence is processed so as to synthesize speech in a method such as a synthesis by rule, thereby sending the obtained speech to the partner. Namely, the system includes a combination of an automatic translation from a first language into a second language and an automatic translation from the second language into the first language, which allows speakers respectively of the first and second languages to conduct voice communications in their own languages.
However, (1) since the automatic translation technology has not been completely developed, the translations cannot be of a satisfactory quality. Among various difficulties of the quality of translation, lexical selection is regarded as a fundamental problem.
That is, a wrong lexical selection frequently occurs because of misjudgment of a word with multiple meanings in a sentence.
For example, an English word "bank" to be interpreted as a Japanese equivalent "teibo" is erroneously translated as a Japanese word "ginko". (2) Terminological inconsistency is another problem which is caused in a communicating system with translating function including the automatic translation from the first language into the second language and the automatic translation from the second language into the first language. Namely, a word representing a concept may possibly be changed through the translations in the respective directions.
For example, a Japanese word "teibo" from a Japanese speaker is interpreted as an English equivalent "bank" through a Japanese-English translation. Thereafter, in association with a sentence including the word "bank", when an English speaker sends a sentence containing the word "bank", the system may translate the word "bank" into a Japanese equivalent "dote" through an English-Japanese translation. Due to occurrences of the mistranslation and the terminological inconsistency, the communication systems with translating function above are attended with the problems when put to practical uses.
In order to solve the problems above, the JP-A-1-251276 has disclosed a communication system with translating function developing a bi-directional translation. In this system, there are stored pairs of words or equivalents attained in a process of translation from a first language into a second language i.e. translation relationships between words of the first language and their equivalents in the second language. When translating a sentence in a reverse direction, namely, in a translation of a sentence expressed in the second language into the first language, the translation relationships thus stored are referenced to select equivalents in the second language for the words of the first language sentence. In short, the publication of this technology has proposed operations and constitutions associated therewith in which the translation relationships collected through a translation procedure in a direction are employed when a translation is achieved in a reverse direction. However, it has a defect that the translation relationships collected through a translation procedure are not always appropriate for translation in the reverse direction. Assume that a first language word A is mistranslated into a second language word X and a second language speaker uses a word Y to express the same concept as that of A. The collected translation relationship (A, X) will be useless for translation in the reverse direction. Though the desirable relationship is (A, Y), it cannot been collected.